Advanced Diagnostics

DTC P0161: Front Secondary Heated oxygen Sensor (Secondary HO2S (Bank 2, Sensor 2)) Heater Circuit Malfunction




General Description
A heater for the zircon element is embedded in the front secondary heated oxygen sensor (front secondary HO2S (bank 2, sensor 2)) and is controlled by the engine control module (ECM)/powertrain control module (PCM). When activated, it heats the sensor to stabilize and speed up the detection of oxygen content when the exhaust gas temperature is cold.

If the front secondary HO2S heater draws more or less than a specified amperage, the ECM/PCM detects a malfunction and stores a DTC.




Monitor Execution, Sequence, Duration, DTC Type, OBD Status




Enable Conditions

Malfunction Threshold
The front secondary HO2S heater output is 0.38 A or less, or 3.33 A or more, for at least 5 seconds when the heater is on.

Driving Pattern
1. Start the engine. Let it idle until the radiator fan comes on.
2. Drive the vehicle at a steady speed of 35 mph (57 km/h) or more for at least 5 seconds.

Diagnosis Details

Conditions for illuminating the MIL
When a malfunction is detected, the MIL comes on and the DTC and the freeze frame data are stored in the ECM/PCM memory.

Conditions for clearing the MIL
The MIL will be cleared if the malfunction does not recur during three consecutive trips in which the diagnostic runs.

The MIL, the DTC, and the freeze frame data can be cleared by using the scan tool Clear command or by disconnecting the battery.